So yesterday BA announced that they will start codesharing with Vistara in four weeks. From September 27th onward you will be able to fly with BA Chennai, Mumbai and Delhi and connect to a Vistara codeshare flight to many secondary Indian cities like Pune or Ahmedabad, etc. (comes in handy with that SQ AMD-SIN-EWR fare ex AMD).

News: British Airways to codeshare with Indian domestic carrier Vistara | Airlines content from ATWOnline

Press release: British Airways - INDIAN SUMMER FOR BRITISH AIRWAYS AS THEY PARTNER WITH DOMESTIC AIRLINE VISTARA

Now my questions:

Has anyone tried booking such flights? So far I can't find any codeshares on Vistara. Haven't the flights been loaded into the GDS at this point? When do you think this will happen at the latest considering the flights are already starting in less than four weeks?